1. Field of the Invention
This invention relates to a combustion turbine power plant and, more specifically, to a combustion turbine power plant having a compressed air steam generator which is coupled to a transition section between the combustor assembly and turbine assembly of the combustion turbine power plant.
2. Background Information
Combustion turbine power plants, generally, have three main assemblies: a compressor assembly, a combustor assembly, and a turbine assembly. A transition section is located between the combustor assembly and the turbine assembly. In operation, the compressor assembly compresses ambient air. The compressed air is channeled into the combustor assembly where it is mixed with a fuel. The fuel is ignited in the combustor assembly creating a heated working gas. The heated working gas passes through the transition section and into the turbine assembly. Within the transition section, the working gas is typically between 2500-2900.degree. F. (1371-1593.degree. C.). The transition section is heated by the working gas to temperatures near its structural limits. Components subjected to such extreme temperatures may degrade due to thermal stress. Therefore, it is advantageous to provide a cooling system to remove heat from the transition section.
A typical cooling apparatus comprises a heat recovery steam generator located in the exit path from the turbine. The heat recovery steam generator is coupled to a water supply. When the combustion turbine is in operation, heated exhaust gas exits the turbine assembly and passes through the heat recovery steam generator converting water into steam. The steam from the heat recovery steam generator is passed through cooling channels within the casing of the transition section. As the steam passes through the transition section it absorbs heat thereby cooling the transition section. This heated steam may be channeled back into the flow path of the combustion turbine to provide power augmentation or may be channeled to a separate steam turbine.
Because the heat recovery steam generator is located in the exhaust path of the combustion turbine, the heat recovery steam generator may not provide a sufficient amount of steam during the start up cycle to cool the transition section of the combustion turbine. Additionally, combustion turbines which rely on a single heat recovery steam generator have to be shut down to perform maintenance operations on the heat recovery steam generator.
There is, therefore, a need for a steam generator to provide steam to a combustion turbine during the start up cycle of the combustion turbine.
There is a further need for a steam generator which could be used in conjunction with a heat recovery steam generator to provide an alternative source of steam when the heat recovery steam generator is undergoing maintenance.
There is a further need for a steam generator which provides an output of both steam and cooled air which may be used to cool the transition section and the turbine section respectively.